BF4 Single player "hard" difficulty too easy

I've recently completed the Battlefield 4 single-player campaign on the PC. I chose hard difficulty, but was amazed how easy the game was. Any opposition you face is absolutely inadequate:

1. Enemy accuracy is abysmal.
2. Enemy reaction time is extremely long.
3. Health regen delay is small and regen speed is high.
4. When enemies use cover, they make sure that their head is sticking out so that you can headshot them - how very convenient.

Overall, the difficulty was so low that I never felt that I am playing an actual game. The situations I was getting into were comical. I could safely reload a gun with an enemy just in front of me and he could not hit me! I am by no means a good player. My multiplayer stats indicate that I am just mediocre. But I cannot remember another first-person shooter that was so easy on the hardest difficulty setting.

I have two possible explanations:
1. Due to some bug I've actually played on easier difficulty. But battlelog indicates that I've completed everything on hard.
2. Difficulty balance was targeted at console players, not at someone with a mouse.

But I have found a workaround: only use a PDW in a semi-auto mode. Doing so brings difficulty to a more reasonable level.